This is a five year trial to test whether improvements in whole body insulin sensitivity can prevent or delay the development of type 2 diabetes in Hispanic women. Subjects are identified to be at high risk for diabetes by a history of gestational diabetes and by their oral glucose tolerance profile when not pregnant. Subjects are randomized to receive placebo or troglitazone, 300 mg/d for up to five years. The primary outcome variable is the diabetes incidence rate. Additional major outcome variables are pancreatic B-cell function and carotid intimal-medial thickness.